public class CandidateKey {

	// This method acts as a uniqueness checker for the Candidate object based on the Email__c field
	public static void hasCandidateDuplicates(Candidate__c[] candidates){
	
        //TODO: Define a map for unique Candidates called "candidateMap" that maps a String to the Candidate
        Map<String,Candidate__c> candidateMap = new Map<String,Candidate__c>();

		//TODO: Declare a for loop to cycle through the candidates.
		for ( Candidate__c cand : candidates) {
       		// TODO: Within that loop, check to verify that the email is not null and if it has a value, store the lastName+email in a String called "uKey"
			// and then check to see if there are duplicate uKeys within this batch of records.  If there are, use addError to prevent them,
			// and if not, add the uKey/candidate combo to the candidateMap.
			if ( cand.Email__c != null ) {
				String uKey = cand.Last_Name__c + cand.Email__c;
				if ( candidateMap.containsKey(uKey)) {
					cand.addError( 'No way, Jose');
				} else {
					candidateMap.put(uKey, cand);
				}
			}
		}
		
  		//Now hit the DB looking for dupes
  		if (!candidateMap.isEmpty()){
	  		for(Candidate__c[] candidatesCheck:[select Id, unique_key__c from Candidate__c where unique_key__c IN :candidateMap.keySet()]) {
				for(Candidate__c candidate:candidatesCheck) {
	  				String currentCandidateId = candidate.Id;
	  				//if there's a dupe and this isn't the current record, then add the error.
	  				if(candidateMap.containsKey(candidate.unique_key__c) && (currentCandidateId != candidateMap.get(candidate.unique_key__c).Id)) {
	     				candidateMap.get(candidate.unique_key__c).addError('Duplicate LastName + Email found in salesforce(id: ' + candidate.id + ')');
	  				}
	  			}
	    		}
  		} 
  	} 
}